With recent expansion of therapies using molecular target drugs, typically antibody drugs, quantitative determination of a biological substance (antigen) on target cells has been required for more effective design of molecular target drugs. A known method for detecting a biological substance is tissue analysis based on binding of a fluorescent substance having a biological substance recognizing site and a biological substance reactive to the biological substance recognizing site.
Patent Literature 1 proposes a method of staining a tissue with a phosphor having a biological substance recognizing site, and determining the number of fluorescent bright spots and the intensity of fluorescent light from the average luminance per particle calculated through analysis of peaks in the luminance distribution of the fluorescent bright spots to evaluate the expression level of the biological substance.